U.S. Pat. No. 4,218,240 to Gingerich, et al. relates to a process wherein cobalt is recovered by treating aqueous solutions containing ammonia and cobalt irons with sufficient amount of an acid in the presence of a catalyst to convert the cobalt irons to a cobalt hexammine ion which is precipitated and separated from the resulting solution. The precipitate is dissolved in an aqueous solution to form a relatively pure solution which is treated with a metallic hydroxide to form a cobalt containing precipitate which is reduced to form fine particles of cobalt.
According to the above basic process, some copper may be removed during the normal purification steps during filtration of the aqueous cobaltic hexammine solution. If small amounts of ammonium chloride and ammonium hydroxide are present in the aqueous hexammine cobalt chloride solution, some of the copper remains dissolved and contaminates the cobalt hexammine precipitate.
Typically the scrap material contains significant quantities of copper and silver which are commonly used in brazing alloys. In this case, the normal purification step may be achieved with difficulty due to the presence of large quantities of solids.